1. Field of the Invention
The present invention is directed to a solenoid actuated flow control controller valve for a fuel system. In particular, the present invention is directed such a flow control controller valve with armature overtravel.
2. Description of Related Art
Electromagnetically actuated control valves are widely used in fuel injectors and timing fluid/injection fuel metering systems for precisely controlling the timing and metering of the injected fuel as well as timing fluid. Precise control of the timing and metering of fuel as well as timing fluid is necessary to achieve maximum efficiency of the fuel system of an internal combustion engine. This requires valve designers to consider these performance requirements in their designs. In addition, valve designers continually attempt to reduce the size of the control valves to reduce the overall size and weight of the engine and permit the control valves to be easily mounted in a variety of locations on the engine without exceeding packaging restraints.
Another concern of valve designers is valve seat wear and valve bounce. Control valves are often operated by a solenoid type actuator assembly. The response time of the controller valve has been decreased by improving the de-energizing response time of the actuator. However, as a result, the valve device closing velocity is increased resulting in increased impact forces on the valve seat. These high impact forces of the valve device against a valve seat cause excessive seat stresses, valve seat beating, and excessive wear. Moreover, when the valve impacts the valve seat at a high velocity, the valve tends to bounce off the seat adversely affecting the control of fluid flow and causing additional valve seat wear.
U.S. Pat. No. 6,056,264 issued to Benson et al. and assigned to the assignees of the present invention discloses a solenoid actuated controller valve that includes a valve plunger, a solenoid actuator with a coil and an armature, and an armature overtravel feature that permits continued movement of the armature relative to the valve plunger from an engaged position, into a disengaged position, when the valve plunger reaches a closed position. The armature overtravel feature includes an overtravel biasing spring for returning the armature from the disengaged position to the engaged position prior to subsequent energization of the actuator coil. As a result, the overtravel feature minimizes the mass impacting the valve seat thereby extending valve seat life while avoiding lost motion in the armature during the next actuation cycle to thereby minimize valve response time. The reference also discloses the use of an armature stop and fluid film that limits the amount of overtravel.
Thus, Benson et al. provides a significantly improved solenoid actuated flow controller valve which reduces the stress on the valve seat. However, a limitation in the solenoid actuated flow controller valve of Benson et al. is that there is variation in the amount of overtravel by the armature assembly. This can negatively affect the performance of the controller valve. In addition, significant secondary impact has been found to occur as described in further detail below that can also negatively affect the performance of the solenoid actuated controller valve.
U.S. Pat. No. 6,510,841 B1 issued to Stier and assigned to Robert Bosch GmbH discloses a fuel injector that utilizes a two-part armature which can reduce secondary impact and prevent an undesirable secondary short-term opening of the fuel injector. However, this reference does not disclose a fuel injector in which the armature assembly is decoupled from the valve needle or plunger. Thus, this reference does not disclose overtravel by the armature assembly to prevent high actuator seat stress.
Consequently, there is a need for a compact, inexpensive flow controller valve that allows overtravel by the armature assembly which avoids the limitations of prior art flow controller valves. In addition, there also exists an unfulfilled need for such a flow controller valve that minimizes the secondary impact.